1. Redistiled phenol: Sigma P1037, for molecular biology, 500ml
2. 1M Tris pH 8
3. pH paper
4. beta-mercaptal ethanol
5. hydroxy-quinoline
6. Pipet
7. Ventilation hood

Warning: Phenol is toxic! wear gloves and operate in chemical hood.

1. Warm redistiled (solid) phenol ( 500ml) in 65C water bath. Check color -> must be colorless!!!  If pink or yellow, do not use.
2. Add equal volume (about 400ml)1M Tris pH8 and mix. Let stand at 4C until phases seperate completely.
3. Remove aqueous phase (top). Add equal volume (400ml) as in step 2 of 0.1M Tris pH8, mix. Let phases seperate as above.
4. Estimate pH of aqueous phase with pH paper (pH meter should not be used or the electrode would be destroyed) should be >= 7.6. If lower, repeate step 3.
5. Remove aqueous. Add 0.1 volume (50ml) of 0.1 M Tris pH8 containing 0.2% beta-mercaptal ethanol, 0.5g/50ml hydroxy-quinoline. (hydroxy-quinoline might be difficult to dissolve, which doesn't matter. After add to phenol all solid will be dissolved).
6. Store at 4C. Shield from light and minimize exposure to ambient atmosphere.

!. To avoid phenol lost, when remove aqeous phase, use modified thin hole (burn and cut) pasteur pipet to asperate and leave 2-3mm aqeous.